In the related art, a probe unit accommodating a plurality of contact probes for electric connection between an inspection target and a signal processing apparatus outputting an inspection signal is used for inspection of a conduction state or operating characteristics of the inspection target such as a semiconductor integrated circuit or a liquid crystal panel. With respect to the probe unit, in the progress in high integration and miniaturization of the semiconductor integrated circuit or the liquid crystal panel of the related art, techniques capable of being adapted to highly integrated, miniaturized inspection target by reducing a pitch between contact probes have progressed.
Under this circumstance, in order to maintain and stabilize electric characteristics of the contact probe, a contact probe where a base portion which is not in contact with an external electrode is formed with a precious metal so as to secure electric stability and a distal end portion which is in contact with the external electrode is formed with different metals or metal alloys so as to suppress an increase in contact resistance due to attachment of an external electrode material and an oxide film of the external electrode material is disclosed (for example, refer to Patent Literature 1).
The contact probe disclosed in Patent Literature 1 is configured to include plungers of which the distal end portions are in contact with respective contact objects and an electrically conductive compression spring in a coil shape, which connects base end portions of the plungers. The compression spring is formed by winding a wire rod at a predetermined pitch, and an electric signal flows through the wire rod. When the distal end portion of each plunger is in contact with the contact object, the plunger exerts a force in the direction opposite to the force exerted from the contact object, so that the contact state between the plunger and the contact object is stabilized.